Ships employ water for a variety of uses, such as drinking, washing and operating the ship. One particularly important use of water in a ship is as ballast water and, because of its great importance, marine ballast water will be used hereinafter to illustrate the invention, it being understood the reference to ballast water throughout this specification is not meant to limit the invention in any way to a use in respect of any specific type of water. Typical types of waters and uses in ships are briefly summarized below:                A) Ballasting—water used to assure ship stability, trim, and effective immersion of ship propellers for efficient propulsion.        B) Washing of tanks, holds, and other cargo spaces. Such sea waters must be cleaned before discharge.        C) Distillation or fresh water—such sea water must be properly treated to assure the effective performance of distillation processes, particularly in low temperature high-vacuum distillers.        D) Sanitary water on ships is always provided by sea water. Shipboard seawater-based sewage requires special treatment of the intake water.        E) Cooling sea water for engines, condensers and other ship-borne equipment. Such waters must be treated for effective operation of the equipment.        F) Bilge and Fuel/Lube Oil Tank washing sea water. Such oily water must be filtered, treated and separated. Treatment can be performed before or after ceasing operation and oil can be separated from the water afterwards.        G) Numerous uses of fresh water, which is stored in fresh water tanks for lengthy periods of time and must be filtered and treated before use to eliminate tank wall contaminants such as water-borne species remaining after washing with sea water.        
The invention is directed, inter alia, to all such types of water and others not mentioned above, and it is not limited to any specific type of water. Whenever reference is made to ballast water, it is meant to cover all such types of waters. It is understood that ballast water is employed only as the representative and non-limiting example of treated water.
As said, a ship without load is usually loaded with ballast water to better balance it. The ballast water is pumped up from the sea at one location, and pumped out back into the sea at another location, according to the need. The release of non-indigenous marine organisms, whether marine organic material, e.g. worms, spores, bacteria, viruses plankton (zooplankton or phytoplankton) or larger organisms, with large volumes of ballast water, can have damaging ecologic and economic consequences, and therefore purification procedures are required. Another problem is a deposit build-up in the ballast tank due to the action of said organic materials and other polluting material waste, particularly microorganisms.
Methods currently used for the purification of ballast water employ nearly all conventional technologies that are used in water purification, and usually relate to the removal of a specific contaminant. Japanese patent publication JP 4322788 relates to a method and device for destroying cysts of harmful algae in ballast water by using a chlorine-based microbiocide or hydrogen peroxide. U.S. Pat. No. 5,256,423 discloses a method for destroying cysts of noxious plankton, comprising introducing hydrogen peroxide into the ballast water to reach a concentration from 10 to 500 ppm, and holding said concentration for a period of 3 to about 48 hours. U.S. patent application Ser. No. 2002/0030011 describes an apparatus and method for treating water to be used as ballast water, comprising the centrifugal separation of sediment, followed by the UV-irradiation of the partially processed water.
The methods relating to a specific contaminant, do not take into consideration the possibility that certain, non-targeted, organisms may have a detrimental effect on the biological habitat because of trans-contaminations by ballast water. On the other hand, large amounts of biocides may present biological hazards, or can damage the ballast water tank in the long term, and therefore long reaction times, involving the presence of relatively highly corrosive species, may be impractical. Some methods cannot be scaled-up to provide a practical means for today's ships which may use tens of thousands of tons of ballast water.
It is an object of the present invention to provide a novel and improved process and system for the purification of water.
It is another object of the invention to provide a process and efficient system for the purification of ballast water which will act on substantially all potentially detrimental organisms.
It is yet another object of the invention to provide a process for the purification of ballast water that can be scaled-up.
It is still another object of the invention to provide a process for the purification of ballast water which does not cause a contamination of the sea pathways by excessive amounts of biocides.
It is a further object of this invention to provide a process for the purification of ballast water which employs the synergistic effect of three combined processes, namely oxidation, filtration, and UV-radiation.
It is still a further object of the present invention to provide a process for the purification of ballast water in which the total concentration of the oxidant in the tank is kept low at all times
The present invention also aims at providing a compact device for the purification of ballast water that can be employed before, after, and during the ship's voyage.
It is also a further object of the invention to provide an apparatus that can be built modularly, to accommodate different or changing needs.
Other objects and advantages of the invention will appear as the description proceeds.